code: def _downgrade_v6(op):
      op.drop_table("equity_supplementary_mappings")
  
file_path: catalyst/catalyst/assets/asset_db_migrations.py
imports: from functools import wraps
  from alembic.migration import MigrationContext
  from alembic.operations import Operations
  import sqlalchemy
  from toolz.curried import do, operator
  from catalyst.assets.asset_writer import write_version_info
  from catalyst.errors import AssetDBImpossibleDowngrade
  from catalyst.utils.preprocess import preprocess
  from catalyst.utils.sqlite_utils import coerce_string_to_eng
label_desc: Use image node_id 9 for calling a global function with example usage: _downgrade_v6(op) without return types